1. Field of the Invention
The present invention relates to a prestressing device, and more particularly to a prestressing device for a mechanical component of a mechanical finishing device to provide a prestressing tension to the mechanical component.
2. Description of Related Art
With reference to FIG. 6, a mechanical finishing device like a lathe, a milling machine or a drilling machine, etc. substantially comprises a base (30), a moving base (40), a work table (50), a column (10) and a tool-head stand (20). The moving base (40) is mounted on a pair of fore and aft tracks (31) on the base (30) and is moveable in a for and aft horizontal direction. The work table (50) is mounted on a pair of side-to-side tracks (41) on the moving base (40) moveably in a side-to-side horizontal direction perpendicular to the fore and aft horizontal direction. Consequently, an object (not shown) can be secured on the work table (50) and moved to a desired position under the tool head stand (20) by means of the movements of the moving base (40) and the work table (50).
The column (10) is secured vertically to one end of the top of the base (30). The tool-head stand (20) is moveable mounted on a longitudinal track on the column (10). Tool heads like milling cutters or bits are rotatably mounted on the tool-head stand (20) to machine the object on the work table (50).
The mechanical components (10, 20, 30, 40, 50) of the mechanical finishing device are always made with casting processes and are extremely heavy. When one of the moveable mechanical components (20, 40, 50) moves to the distal end of the supporting mechanical component (10, 30, 40) on which it is mounted, for example the work table (50) moves to the distal end of the moving base (40) or the tool-head stand (20) moves to the uppermost end of the column (10), the supporting mechanical component (10, 30, 40) is easily bent due to the huge weight of the moving mechanical component (20, 40, 50). In especially, when the mechanical finishing device is used to machine an object with a huge weight, the mechanical components (10, 20, 30, 40, 50) of the mechanical finishing device are easily bent due to the weight of the moving mechanical components (20, 40, 50) and the object on which the mechanical finishing device is working. The mechanical components (10, 20, 30, 40, 50) of the mechanical finishing device are easily deformed and damaged, and the useful life of the mechanical finishing device is shortened. In addition, to enhance the structural strength of each mechanical component (10, 20, 30, 40, 50) to prevent deformation, the thickness of the mechanical component (10,20,30,40,50) is enlarged. However, as the weight of the mechanical components (10, 20, 30, 40, 50) is increased, conventional techniques for preventing deformation become less effective.
To overcome the shortcomings, the present invention provides a prestressing structure to mitigate or obviate the aforementioned problems.
The main objective of the invention is to provide a prestressing device for a mechanical component of a mechanical finishing device to provide a prestressing tension on the mechanical component. The prestressing device has at least one rigid prestressing unit mounted in the mechanical component to provide a prestressing tension to the mechanical component. This can prevent the mechanical component from being bent or deformed when a large force is applied to the mechanical component. The useful life of the mechanical finishing device is prolonged.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.